1. Field of the Invention
The present invention relates to a vehicle detecting method and a vehicle detecting apparatus, and more particularly to a front vehicle detecting method and a front vehicle detecting apparatus.
2. Description of the Related Art
One of the major reasons for traffic accidents is nighttime driving, because the vision of a driver in the nighttime is worse than that in the daytime. In the nighttime driving, it is possible to provide better vision for the driver by a high-beam of the vehicle headlights. On the other hand, the high-beam may have an influence on a driver on the opposite side, and it may bring danger to the driver on the opposite side. It may be rather inconvenient for the driver to switch frequently by hand between high-beam and low-beam.
U.S. Pat. No. 7,512,252B2 discloses a vehicle detecting system, in which a long time exposure and a short time exposure are conducted respectively by an onboard camera so as to obtain two images, and taillights, headlights, and other lights (for example, signal lights or street lights) are identified by using image characteristics in the two images having different exposures.
The above patent (U.S. Pat. No. 7,512,252B2) relies on a condition that in JAPAN traffic keeps to the left and an assumption that the headlight is located in the right side of the image and the taillight is located in the left side of the image; however, as for the practical reality of road conditions, the road is not always straight and the road may have plural lanes, so that the assumption is not always correct. Furthermore, the above patent (U.S. Pat. No. 7,512,252B2) determines whether the light comes from the vehicle or not by comparing the location relationship between a vanishing point and the detected light; however, the assumption is not always correct in the case of an uneven road (for example, a slope). In addition, in the above patent (U.S. Pat. No. 7,512,252B2), the taillight appears only in an image having a long time exposure by controlling exposure intensity; however, the intensity of the light has relationships with both (1) a condition that the light is a headlight or taillight and (2) the distance between the light and the own vehicle. For example, the intensity of the taillight of the vehicle in the near distance may be higher and the light of the taillight of the vehicle in the near distance may be brighter than the headlight of the vehicle beyond. Therefore, the assumption is not always correct.
Furthermore, U.S. Pat. No. 7,429,825B2 discloses a vehicle light control system, comprising: a rear vehicle information catching module for catching the information of a vehicle behind the own vehicle; an overtaking forecasting module for forecasting whether the rear vehicle overtakes the own vehicle or not based on the information of the rear vehicle; a mode change condition determining module for determining whether a predetermined mode change condition is met or not based on the forecasted overtaking; and an automatic mode setting module for bringing out the automatic changeover between the high-beam and the low-beam in cases where the predetermined mode change condition is met.
However, in the vehicle light control system of U.S. Pat. No. 7,429,825B2, the detection based on the white line of the road (lane) in the nighttime merely detects the rear vehicle in the same lane with the own vehicle, but cannot detect the front vehicle of the own vehicle.
Therefore, it is necessary to provide a method and an apparatus by which the front vehicle of the own vehicle can be detected in the nighttime.